Heat exchanger with sacrificial turbulator

ABSTRACT

A heat exchanger is disclosed. The heat exchanger includes a hollow tube extending from a tube inlet to a tube outlet. The hollow tube includes a wall inner surface comprising a copper alloy or a first aluminum alloy. A first fluid flow path is disposed along the wall inner surface from the tube inlet to the tube outlet. A turbulator is disposed within the hollow tube along the first fluid flow path, and the turbulator comprises a second aluminum alloy that is less noble than the copper or first aluminum alloy. A second fluid flow path is disposed across an outer surface of the wall.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Application No. 62/781,935,filed on Dec. 19, 2018, which is incorporated herein by reference in itsentirety.

BACKGROUND

Exemplary embodiments pertain to the art of heat exchangers and, morespecifically, to aluminum alloy heat exchangers.

Heat exchangers are widely used in various applications, including butnot limited to heating and cooling systems including fan coil units,heating and cooling in various industrial and chemical processes, heatrecovery systems, and the like, to name a few. Many heat exchangers fortransferring heat from one fluid to another fluid utilize one or moretubes through which one fluid flows while a second fluid flows aroundthe tubes. Heat from one of the fluids is transferred to the other fluidby conduction through the tube walls. Many configurations also utilizefins in thermally conductive contact with the outside of the tube(s) toprovide increased surface area across which heat can be transferredbetween the fluids, improve heat transfer characteristics of the secondfluid flowing through the heat exchanger and enhance structural rigidityof the heat exchanger. Such heat exchangers include microchannel heatexchangers and round tube plate fin (RTPF) heat exchangers.

Heat exchanger tubes may be made from a variety of materials, includingmetals such as aluminum or copper and alloys thereof. Aluminum alloysare lightweight, have a high specific strength and high thermalconductivity. Due to these excellent mechanical properties, aluminumalloys are used to manufacture heat exchangers for heating or coolingsystems in commercial, industrial, residential, transport,refrigeration, and marine applications. However, aluminum alloy heatexchangers can be susceptible to corrosion. Corrosion eventually leadsto a loss of refrigerant from the tubes and failure of the heating orcooling system. Sudden tube failure results in a rapid loss of coolingand loss of functionality of the heating or cooling system, in additionto the environmentally damaging loss of refrigerant to the environment.Many different approaches have been tried with regard to mitigatingcorrosion and its effects; however, corrosion continues to be aseemingly never-ending problem that needs to be addressed.

BRIEF DESCRIPTION

A heat exchanger is disclosed. The heat exchanger includes a hollow tubeextending from a tube inlet to a tube outlet. The hollow tube includes awall inner surface comprising a copper alloy or a first aluminum alloy.A first fluid flow path is disposed along the wall inner surface fromthe tube inlet to the tube outlet. A turbulator is disposed within thehollow tube along the first fluid flow path, and the turbulatorcomprises a second aluminum alloy that is less noble than the copper orfirst aluminum alloy. A second fluid flow path is disposed across anouter surface of the wall.

In some embodiments, the heat exchanger can further include a shellaround the second flow path and the hollow tube, the shell including aninlet and an outlet in operative fluid communication with the secondfluid flow path.

In any one or combination of the foregoing embodiments, the wall innersurface can comprise the copper alloy.

In any one or combination of the foregoing embodiments, the wall innersurface can comprise the first aluminum alloy.

In any one or combination of the foregoing embodiments, the secondaluminum alloy can include zinc or magnesium.

In any one or combination of the foregoing embodiments, the secondaluminum alloy can include an alloying element selected from tin,indium, gallium, or combinations thereof.

In any one or combination of the foregoing embodiments, the hollow tubewall can be arranged as a hollow cylinder around the first fluid flowpath.

In any one or combination of the foregoing embodiments, the heatexchanger can further include a plurality of fins comprising a thirdaluminum alloy extending outwardly from an outer surface of the wall.

Also disclosed is a heat transfer system comprising a heat transferfluid circulation loop in operative thermal communication with a heatsource and a heat sink, wherein the heat exchanger of any one orcombination of the foregoing embodiments is disposed as a thermaltransfer link between the heat transfer fluid and the heat sink or heatsource.

In some embodiments, the heat transfer fluid circulation loop can be inoperative fluid communication with the first fluid flow path.

In any one or combination of the foregoing embodiments, the heattransfer fluid of the heat transfer system can comprise water.

In any one or combination of the foregoing embodiments, the heattransfer fluid of the heat transfer system can comprise alcohols,glycols, chlorides, formats/acetates, or ammonia.

In any one or combination of the foregoing embodiments, the heattransfer fluid of the heat transfer system can comprise ethylene glycolor propylene glycol.

Also disclosed is a heat transfer system that includes a first heattransfer fluid circulation loop in thermal communication with a heatsink, comprising a refrigerant in operative fluid communication with aheat absorption side of a cross-over heat exchanger. A second heattransfer fluid circulation loop is in thermal communication with a heatsource, and comprises an aqueous heat transfer liquid in operative fluidcommunication through a hollow tube including a wall inner surface thatcomprises a copper alloy or a first aluminum alloy on a heat rejectionside of the cross-over heat exchanger. The hollow tube further includesa turbulator disposed within the hollow tube comprising a secondaluminum alloy that is less noble than the copper or first aluminumalloy.

In some embodiments, the first heat transfer fluid circulation loop ofthe heat transfer system can include a compressor, a heat rejection heatexchanger in thermal communication with the heat sink, an expansiondevice, and the heat absorption side of the cross-over heat exchanger,connected together in order by conduit.

In any one or combination of the foregoing embodiments, the heattransfer system can be configured to reduce the aqueous heat transferliquid below 0° C.

In any one or combination of the foregoing heat transfer systemembodiments, the aqueous heat transfer liquid can comprise alcohols,glycols, chlorides, formats/acetates, or ammonia.

In any one or combination of the foregoing heat transfer systemembodiments, the wall inner surface can comprise the copper alloy.

In any one or combination of the foregoing heat transfer systemembodiments, the second aluminum alloy can include zinc or magnesium.

In any one or combination of the foregoing heat transfer systemembodiments, the second aluminum alloy can include an alloying elementselected from tin, indium, gallium, or combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 shows a perspective view of portions of a tube in shell heatexchanger;

FIGS. 2A, 2B, and 2C show views of a heat exchanger tube and turbulator;

FIG. 3 shows a perspective view of portions of a round tube plate finheat exchanger; and

FIG. 4 schematically shows a heat transfer system.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Referring now to FIG. 1, an example embodiment of a heat exchanger 36with tubes and turbulator is such as can be used in a dual circuitrefrigerant cycle using two heat transfer fluid passes. The heatexchanger is of the tube and shell variety, but other configurations canbe used as discussed in greater detail below. As shown in FIG. 1, heattransfer fluid flows through a plurality of copper tubes 38 andrefrigerant surrounds the tubes 38 positioned within a shell 40,exchanging heat. A center partition plate 42 perpendicular to the axisof the shell 40 separates refrigerant circuit A and refrigerant circuitB. The partition plate 42 includes a plurality of apertures 44 toreceive the plurality of tubes 38. A pass partition plate 82perpendicular to the center partition plate 42 separates the heattransfer fluid passes Y1 and Y2.

Heat transfer fluid from a first refrigerant box 80 enters pass Y1.Inlet heat transfer fluid enters the refrigerant circuit A through theplurality of tubes 38 and exchanges heat with refrigerant circuit A.Refrigerant of refrigerant circuit A enters the shell 40 through inlet46 and exits the shell 40 through outlet 48. Although the inlet 46 isillustrated at the bottom surface, the inlet 46 can be positioned atother locations in other type evaporators. Heat transfer fluid thenenters and exchanges heat with the second refrigerant circuit B.Refrigerant of refrigerant circuit B enters the shell 40 through inlet50 and exits the shell 40 through outlet 52. The heat transfer fluidfrom Y1 then enters a heat transfer fluid box 54. The heat transferfluid then enters pass Y2 through tubes 48 and passes again throughrefrigerant circuits A and B. In the prior art design, the tubes 38 areof substantially the same diameter. Additionally, in some embodimentsboth refrigerant circuits A and B include an equal number of tubes.

As mentioned above, in some embodiments the tubes 38 are made of copperor a copper alloy, or of a first aluminum alloy. Alternatively, thetubes 38 can be clad with or have surface portions thereof covered withthe copper or first aluminum alloy. Copper alloys, if present, for thetubes 38 can be selected from any of a number of known alloys, includingbut not limited to C120 or C122 (copper alloy numbers according to theUnified Numbering System for Copper+Copper Alloys, administered by theAmerican National Standards Institute and the American Society forTesting and Materials. The first aluminum alloy, if present, can be analuminum alloy based material and, in some embodiments, may be made fromaluminum alloys selected from 1000 series, 3000 series, 5000 series, or6000 series aluminum alloys (as used herein, all alloy numbers and alloyseries numbers and individual alloy numbers are as specified andpublished by The Aluminum Association). Examples of aluminum alloys thatcan be used as core materials include but are not limited to AA1100,AA1145, AA3003, AA3102, AA5052, AA7072, AA8005, or AA8011.

As mentioned above, the tubes 38 include turbulators therein. In someembodiments, the turbulator can take the form of a helical structure(e.g., a double helix as shown in FIGS. 2A-2C or a single helix) thatextends along the length of the tube (i.e., the tube axis), which can beformed by twisting a flat metal tape-like sheet into the desired shape.An example embodiment of a tube 38 with a turbulator therein is shown inFIGS. 2A-2C. As shown in FIG. 2A, a turbulator 39 extends lengthwisealong the inside of the tube 38. A helical turbulator such as theturbulator 39 can be characterized by a period length H (FIG. 2A) and athickness δ. The turbulator can be formed by securing one or more flatmetal tape-like sheets to an end tab 41 (FIG. 2C), and twisting the tapeunder tension relative to the end tab 41, and then inserting the twistedturbulator 41 structure into the tube 38.

The turbulators can be formed from (or be clad with or have surfaceportions thereof covered with) a second aluminum alloy. In embodimentswhere the second aluminum alloy is used as a cladding or surfacecovering, it can be deposited using various techniques including but notlimited to thermal spray (e.g., cold spray), brazing, roll cladding,electroplating, etc. The second aluminum alloy can be an aluminum alloybased material and, in some embodiments, may be made from aluminumalloys selected from 1000 series, 3000 series, 5000 series, or 6000series aluminum alloys, including AA1100, AA1145, AA3003, AA3102,AA5052, AA7072, AA8005, or AA8011. The second aluminum alloy is lessnoble than the copper alloy or is less noble first aluminum alloy,depending on which metal the tube 38 is made of. By “less noble”, it ismeant that the second aluminum alloy is galvanically less noble, i.e.,that the second alloy has a lower galvanic potential or a lowerelectrode potentials than the first aluminum alloy such that the secondaluminum alloy would be anodic with respect to the first aluminum alloyin a galvanic cell. This allows the second aluminum alloy to providesacrificial corrosion protection to the first aluminum alloy. In someembodiments, the difference in galvanic potential between the secondaluminum alloy, and the nearest potential of the first and secondaluminum alloys is in a range having a lower end of >0 V, 50 mV, or 150mV, and an upper end of 400 mV, 650 mV, or 900 mV. These range endpointscan be independently combined to form a number of ranges, and eachpossible combination is hereby expressly disclosed. In some embodiments,the second aluminum alloy can be provided with reduced nobility byincorporating alloying elements such as zinc or magnesium. In someembodiments where zinc is present, the zinc can be present in the secondaluminum alloy at a level in a range with a lower end of 0.5 wt. %, 2.0wt. %, 2.5 wt. %, or 4.0 wt. %, and an upper end of 4.5 wt. %, 6.0 wt.%, 7.0 wt. %, or 10.0 wt. %. These range endpoints can be independentlycombined to form a number of ranges, and each possible combination ishereby expressly disclosed. In some embodiments where magnesium ispresent, the magnesium can be present in the second aluminum alloy at alevel in a range with a lower end of 0.5 wt. %, 1.0 wt. %, or 2.2 wt. %,and an upper end of 1.5 wt. %, 2.8 wt. %, or 4.9 wt. %. These rangeendpoints can be independently combined to produce different ranges,each of which is hereby explicitly disclosed. The second aluminum alloyalso includes one or more alloying elements selected from tin, indium,or gallium. In some embodiments, the selected alloying element(s) can bepresent in the second aluminum alloy at a level in a range with a lowerend of 0.010 wt. %, 0.016 wt. %, or 0.020 wt. %, and an upper end of0.020 wt. %, 0.035 wt. %, 0.050 wt. %, or 0.100 wt. %. These rangeendpoints can be independently combined to produce different possibleranges, each of which is hereby explicitly disclosed (i.e., 0.010-0.020wt. %, 0.010-0.035 wt. %, 0.010-0.050 wt. %, 0.010-0.100 wt. %,0.016-0.020 wt. %, 0.016-0.035 wt. %, 0.016-0.050 wt. %, 0.016-0.100 wt.%, 0.020-0.020 wt. %, 0.020-0.035 wt. %, 0.020-0.050 wt. %, 0.020-0.100wt. %). The second aluminum alloy can also include one or more otheralloying elements for aluminum alloys. The second alloy can also includeone or more other alloying elements for aluminum alloys. In someembodiments, the amount of any individual other alloying element canrange from 0-1.5 wt. %. In some embodiments, the total content of anysuch other alloying elements can range from 0-2.5 wt. %. Examples ofsuch other alloying elements include Si, Fe, Mn, Cu, Ti, or Cr. In someembodiments, the second aluminum alloy can have a composition consistingof: 4.0-6.0 wt. % zinc or magnesium, 0.001-0.1 wt. % of one or morealloying elements selected from tin, indium, gallium, or combinationsthereof, 0-2.5 wt. % other alloying elements, and the balance aluminum.

As mentioned above, other types of heat exchangers (e.g., round tubeplate fin, or microchannel heat exchangers) can include turbulatorsaccording to the present disclosure. An example embodiment of a roundtube plate fin heat exchanger is schematically shown in FIG. 3. As shownin FIG. 3, a heat exchanger 300 can include one or more flow circuitsfor carrying refrigerant. For the purposes of explanation, a portion ofthe heat exchanger 300 is shown with a single flow circuit refrigeranttube 320 in FIG. 3 consisting of an inlet line 330 and an outlet line340. The inlet line 330 is connected to the outlet line 340 at one endof the heat exchanger 300 through a 90 degree tube bend 350. It shouldbe evident, however, that more circuits may be added to the unitdepending upon the demands of the system. For example, although tubebend 350 is shown as a separate component connecting two straight tubesection, the tube 320 can also be formed as a single tube piece with ahairpin section therein for the tube bend 350, and multiple units ofsuch hairpin tubes can be connected with u-shaped connectors at the openends to form a continuous longer flow path in a ‘back-and-forth’configuration. Alternatively, the tubes can be configured as separatetube segments in parallel between headers on each end (not shown). Theheat exchanger 300 can further include a series of fins 360 comprisingradially disposed plate-like elements spaced along the length of theflow circuit, typically connected to the tube(s) 320 with aninterference fit. The fins 360 are provided between a pair of end platesor tube sheets 370 and 380 and are supported by the lines 330, 340 inorder to define a gas flow passage through which conditioned air passesover the refrigerant tube 320 and between the spaced fins 360. Fins 360can also include heat transfer enhancement elements such as louvers. Insome embodiments, fins 360 can be formed from a third aluminum alloy,which can include aluminum alloy materials such as, for example,materials selected from the 1000 series, 3000 series, 6000 series, 7000series, or 8000 series aluminum alloys. The embodiments described hereinutilize an aluminum alloy for the fins of a tube-fin heat exchangerhaving an aluminum alloy tube. In some embodiments, the fins can be madefrom or can be overlaid by an aluminum alloy that is galvanically lessnoble than the tube alloy.

The heat exchanger embodiments disclosed herein can be used in a heattransfer system. Referring now to the FIG. 4, an exemplary heat transfersystem for use as a chiller is schematically shown in block diagramform. As shown in FIG. 4, a first refrigerant circulation loop includesa compressor 410, which pressurizes a refrigerant (e.g., a fluorocarbon)in its gaseous state, which both heats the fluid and provides pressureto circulate it throughout the system. The hot pressurized gaseousrefrigerant exiting from the compressor 410 flows through conduit 415 toheat rejection heat exchanger 420, which functions as a heat exchangerto transfer heat from the refrigerant to the surrounding environment,resulting in condensation of the hot gaseous refrigerant to apressurized moderate temperature liquid. The liquid refrigerant exitingfrom the heat rejection heat exchanger 420 (e.g., a condenser) flowsthrough conduit 425 to expansion valve 430, where the pressure isreduced. The reduced pressure liquid refrigerant exiting the expansionvalve 430 flows through conduit 435 to a heat absorption side (e.g.,evaporator side) of a cross-over heat exchanger 440, which functions asa heat exchanger to absorb heat from a heat transfer fluid, therebycooling or chilling the heat transfer fluid) on a heat rejection side ofthe cross-over heat exchanger 440, thereby cooling or chilling the heattransfer fluid, and causing the refrigerant to boil. The now gaseousrefrigerant exiting the cross-over heat exchanger 440 flows throughconduit 445 to the compressor 410, thus completing the refrigerant loop.The heat transfer system has the effect of transferring heat from theheat transfer fluid on the heat rejection side of the cross-over heatexchanger 440 to the heat absorption side of the heat rejection heatexchanger 420. The thermodynamic properties of the refrigerant allow itto reach a high enough temperature when compressed so that it is greaterthan the temperature on the heat absorption side of the heat exchanger420, allowing for heat transfer. The thermodynamic properties of therefrigerant must also have a boiling point at its post-expansionpressure that provides a temperature differential to cool the heattransfer fluid on the heat rejection side of the cross-over heatexchanger 440 and provide heat at a temperature to vaporize the liquidrefrigerant. The heat exchanger and turbulator embodiments describedherein can be used for either of the heat exchangers 420 or 440. In someembodiments, the heat exchanger and turbulator embodiments describedherein are used for the cross-over heat exchangers 440, wheresacrificial corrosion protection provided by the less noble turbulatorcan protect against conductive and corrosive properties of brines usedas low temperature heat transfer fluids used in some chiller systems.

The heat transfer system shown in FIG. 4 can be used as an airconditioning system, in which the exterior of heat rejection heatexchanger 20 is contacted with air in the surrounding outsideenvironment and the heat absorption heat exchanger 40 is contacted withair in an interior environment to be conditioned. Additionally, as isknown in the art, the system can also be operated in heat pump modeusing a standard multiport switching valve to reverse refrigerant flowdirection and the function of the condensers and evaporators, i.e. thecondenser in a cooling mode being evaporator in a heat pump mode and theevaporator in a cooling mode being the condenser in a heat pump mode.Additionally, while the heat transfer system shown in FIG. 4 hasevaporation and condensation stages for highly efficient heat transfer,other types of refrigerant loops are contemplated as well, such as fluidloops that do not involve a phase change, for example, multi-loopsystems such as commercial refrigeration or air conditioning systemswhere a non-phase change loop thermally connects one of the heatexchangers in an evaporation/condensation loop like FIG. 4 to other heattransfer fluid loops in thermal communication with a surrounding outsideenvironment or to an interior environment to be conditioned.

With continued reference to FIG. 4, the heat transfer system includes aheat transfer fluid circulation loop 450 that utilizes one or more pumps(not shown) to circulate a heat transfer fluid between the heatabsorption side of the cross-over heat exchanger 440 and a heat source455. In some embodiments, the heat transfer fluid in the loop 450 isaqueous, either water or a solution comprising water. In someembodiments, the system can be configured to cool the heat transferfluid in the loop 450 to a temperature at or below 0° C., for example toprovide a freezing temperature to a heat source 455 such as a frozenstorage environment or an ice surface such as an ice rink. For such lowtemperature applications, an aqueous heat transfer fluid can includecomponents to provide the aqueous fluid with a freezing point below 0°C. or below a minimum operating temperature of the cross-over heatexchanger 440. Such low-temperature aqueous heat transfer fluids aresometimes referred to as “brines”, and can include water-soluble organicsolvents such as alcohols, including but not limited to glycols (e.g.,ethylene glycol, propylene glycol), chlorides (e.g., calcium chloride,sodium chloride, potassium chloride, lithium chloride), alcohols(methanol, ethanol and water), potassium (potassium acetate, potassiumformate), and ammonia. Such components can increase electricalconductivity of the aqueous heat transfer fluid, which can promotesusceptibility to galvanic corrosion that is addressed by sacrificialcorrosion of the turbulators to provide a technical effect of protectingthe tube walls. In some embodiments, another heat transfer fluid loop460 can transfer heat from the heat absorption side of the heatexchanger 420 by circulating (pumps not shown) a heat transfer fluid toa heat sink 465 (e.g., a cooling tower in fluid and thermalcommunication with an outside environment (i.e., outside air)). In suchan example embodiment, the heat transfer fluid 460 can include anaqueous heat transfer fluid, which can include optional additives suchas corrosion inhibitors, pH buffers, anti-scale agents, biocides, etc.,but which does not require freezing point suppression like the heattransfer fluid in the loop 450.

To the extent used herein, the term “about” is intended to include thedegree of error associated with measurement of the particular quantitybased upon the equipment available at the time of filing theapplication. For example, “about” can include a range of ±8% or 5%, or2% of a given value.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

1. A heat exchanger comprising: a hollow tube extending from a tubeinlet to a tube outlet, said hollow tube including a wall inner surfacecomprising a copper alloy or a first aluminum alloy; a first fluid flowpath along the wall inner surface from the tube inlet to the tubeoutlet; a turbulator disposed within the hollow tube along the firstfluid flow path, said turbulator comprising a second aluminum alloy thatis less noble than the copper or first aluminum alloy; a second fluidflow path across an outer surface of the wall.
 2. The heat exchanger ofclaim 1, further comprising a shell around the second flow path and thehollow tube, the shell including an inlet and an outlet in operativefluid communication with the second fluid flow path.
 3. The heatexchanger of claim 1, wherein the wall inner surface comprises thecopper alloy.
 4. The heat exchanger of claim 1, wherein the wall innersurface comprises the first aluminum alloy.
 5. The heat exchanger ofclaim 1, wherein the second aluminum alloy includes zinc or magnesium.6. The heat exchanger of claim 1, wherein the second aluminum alloyincludes an alloying element selected from tin, indium, gallium, orcombinations thereof.
 7. The heat exchanger of claim 1, wherein thehollow tube wall is arranged as a hollow cylinder around the first fluidflow path.
 8. The heat exchanger of claim 1, further comprising aplurality of fins comprising a third aluminum alloy extending outwardlyfrom an outer surface of the wall.
 9. A heat transfer system comprisinga heat transfer fluid circulation loop in operative thermalcommunication with a heat source and a heat sink, wherein the heatexchanger of claim 1 is disposed as a thermal transfer link between theheat transfer fluid and the heat sink or heat source.
 10. The heattransfer system of claim 9, wherein the heat transfer fluid circulationloop is in operative fluid communication with the first fluid flow path.11. The heat transfer system of claim 9, wherein the heat transfer fluidcomprises water.
 12. The heat transfer system of claim 9, wherein theheat transfer fluid comprises alcohols, glycols, chlorides,formats/acetates, or ammonia.
 13. The heat transfer system of claim 12,wherein the alcohol comprises ethylene glycol or propylene glycol.
 14. Aheat transfer system comprising: a first heat transfer fluid circulationloop in thermal communication with a heat sink, comprising a refrigerantin operative fluid communication with a heat absorption side of across-over heat exchanger; a second heat transfer fluid circulation loopin thermal communication with a heat source, comprising an aqueous heattransfer liquid in operative fluid communication through a hollow tubeincluding a wall inner surface that comprises a copper alloy or a firstaluminum alloy on a heat rejection side of the cross-over heatexchanger, said hollow tube further including a turbulator disposedwithin the hollow tube comprising a second aluminum alloy that is lessnoble than the copper or first aluminum alloy.
 15. The heat transfersystem of claim 14, wherein the first heat transfer fluid circulationloop includes a compressor, a heat rejection heat exchanger in thermalcommunication with the heat sink, an expansion device, and the heatabsorption side of the cross-over heat exchanger, connected together inorder by conduit.
 16. The heat transfer system of claim 14, wherein thesystem is configured to reduce the aqueous heat transfer liquid below 0°C.
 17. The heat transfer system of claim 14, wherein the aqueous heattransfer liquid comprises alcohols, glycols, chlorides,formats/acetates, or ammonia.
 18. The heat transfer system of claim 14,wherein the wall inner surface comprises the copper alloy.
 19. The heattransfer system of claim 14, wherein the second aluminum alloy includeszinc or magnesium.
 20. The heat transfer system of claim 14, wherein thesecond aluminum alloy includes an alloying element selected from tin,indium, gallium, or combinations thereof.